Information exchange is conventionally protected by encryption of the message, whereas the carrier itself is most often left unprotected for all to see, on the assumption that the information is rendered safe from extraction by unauthorized interceptors. Current advances in computer technology and processing power continue to drastically shorten the time required to decrypt all but the most complex encoding, such that only time-sensitive messages with no enduring value will be safe. Complex information encryption schemes typically increase overhead, slowing message transmission. Conventionally, encryption keys must be exchanged by communicants, thus rendering the encryption more vulnerable than ever. Furthermore, the knowledge that messages are actually being transmitted and/or exchanged is often of value and, where radio is used as the transmission medium, the radio signature itself provides a wealth of location, traffic, and source information. Such signals are easily intercepted, exploited and jammed, if desired, or used for radio location to be exploited in other ways.
Numerous schemes have also been devised to hide radio transmissions below the level of the ambient additive white Gaussian Noise (AWGN), and to secure the waveform itself using direct sequence spread spectrum (DSSS) technology and introduction of other pseudo-random elemental variations.
In prior and contemporary art, while addition of these variations add to the complexity of the waveform, signal intelligence (SIGINT) signal feature extraction methodology, enabling signal reconstruction, has kept pace with these incremental advances. Accurate timing synchronization is generally required prior to and during communications to both facilitate and maintain communications, when using such technology. Furthermore the incremental advances of communications security, (COMSEC), and SIGINT appear to follow a path of diminishing returns.